How to Detect and Fix Memory Leaks in React Native? (With Code & GitHub)

Memory leaks are one of the most dangerous and least visible problems in React Native apps.

A memory leak happens when your app keeps using memory it no longer needs, instead of releasing it properly.

This unused memory keeps growing, silently slowing down your app. In React Native, memory leaks don’t break the app immediately.

Instead, they cause gradual performance degradation, making them harder to detect during development.

Impact of React Native Memory Leaks

• Sudden app crashes after long usage.
• Frozen UI and delayed screen transitions.
• Increased battery consumption.
• Poor user experience and bad app reviews.

Many apps reach production with hidden React Native memory leaks because they don’t appear during short testing sessions.

Without proper React Native performance optimization, these issues only surface when real users start navigating the app continuously.

In this blog, you will learn how to detect and fix memory leaks in React Native.

How Does Memory Management Work in React Native?

To understand memory leaks, you first need to understand how React Native manages memory internally.

JavaScript Thread vs Native Memory

• React Native runs JavaScript code on a JS thread, while UI components and native modules run on the native side (Android/iOS).
• Memory leaks can happen on either side or, even worse, between both.

Role of Hermes and Garbage Collection

• Hermes is a JavaScript engine optimized for React Native. It uses Garbage Collection (GC) to free unused objects.
• GC only works when objects are no longer referenced.

This is why developers often see leaks even when JavaScript “cleans up” references that still exist somewhere.

Using Hermes memory profiling, React Native tools help you understand what’s actually retained in memory & how to profile memory usage in React Native apps correctly.

What Are the Most Common Causes of Memory Leaks in React Native Apps?

Most memory leaks come from small mistakes repeated across the app. These are the leak sources you’ll see in real-world React Native projects:

Leak Sources You’ll See in Real Apps

• useEffect cleanup missing or incorrect, causing retained subscriptions.
• Event listeners not removed properly, leading to event listeners leaking & React Native issues.
• Timers, intervals, and background tasks are running after components are unmounted.
• Large images and unoptimized FlatLists are consuming unnecessary memory.
• Global state retaining references longer than needed.

The most common issue is a useEffect cleanup memory leak, where cleanup functions are forgotten or implemented incorrectly.

How Can You Detect Memory Leaks in React Native Before Users Do?

Detecting leaks early is the key to building stable apps. Instead of waiting for crashes, you should actively detect memory leaks in React Native during development.

Detection Techniques That Actually Work

• Navigation stress testing: Rapidly switch screens to expose retained memory.
• Monitoring memory growth patterns: Memory should stabilize & not continuously increase.
• Heap snapshot comparison: Take snapshots before and after navigation flows.

If memory keeps increasing without going down, you’re likely facing a memory leak detection React Native problem that must be fixed before release.

What Are the Best Tools to Find Memory Leaks in React Native Apps?

Using the right tools makes memory debugging much easier.

Memory Leak Tools for React Native

• Flipper memory profiling React Native: Visualize memory usage and detect spikes.
• Android Studio Memory Profiler: Track Java/Kotlin heap usage.
• Xcode Instruments (Leaks & Allocations) for iOS.
• Hermes debugging tools for JS heap analysis.

These tools help identify leaks on both JavaScript and native layers to make them necessary memory leak tools for React Native apps.

How to Detect Memory Leaks in React Native Using Flipper? (Step-by-Step)

Flipper is one of the best tools to detect memory leaks in React Native, especially when using Hermes.

If you want to understand how to detect memory leaks in React Native with Flipper, follow this exact process.

Step 1: Setting Up Flipper Correctly

Most React Native projects already include Flipper in development mode.

Enable Hermes (Recommended)

Hermes gives better memory insights.

            
                // android/app/build.gradle
                project.ext.react = [
                enableHermes: true
                ];
            
        

Then rebuild the app:

            
                cd android
                ./gradlew clean
                cd ..
                npx react-native run-android

            
        

Install Flipper desktop app and open your running app. Make sure the Memory plugin is enabled.

Step 2: Reading Memory Graphs in Flipper

Once your app is running:

1. Open Flipper → Memory Plugin
2. Start navigating through your app.
3. Watch the JS Heap and Native memory graphs.

Healthy behavior:

• Memory rises slightly, then drops after navigation.

Leak behavior:

• Memory keeps growing and never goes down.

This is the first clear sign of React Native memory leak detection.

Step 3: Identifying Abnormal Memory Spikes

To expose leaks faster, do a navigation stress test:

• Open Screen A
• Navigate to Screen B
• Go back
• Repeat this 10 to 20 times

If memory usage increases on every navigation, you likely have:

• Missing cleanup
• Retained listeners
• Active timers

This method is extremely effective for detecting memory leaks in React Native before users do.

Step 4: Comparing Heap Snapshots (Most Important Step)

1. Take a heap snapshot on Screen A
2. Navigate away
3. Take another snapshot
4. Compare retained objects

If components, listeners, or objects remain in memory after unmount, you’ve found a real memory leak.

This is the most reliable way to profile the memory usage of React Native apps using Flipper.

How to Fix Memory Leaks in React Native? (Real Code)

Now let’s fix the most common leaks using clean, reusable code. These are real React Native memory leak fix code examples you can directly use.

1. Correct useEffect Cleanup Patterns (With Code)

Problematic Code (Memory Leak)

            
                useEffect(() => {
                const interval = setInterval(() => {
                    console.log('Running...');
                }, 1000);
                }, []);
            
        

Fixed Code (No Leak)

            
                useEffect(() => {
                const interval = setInterval(() => {
                    console.log('Running...');
                }, 1000);
                
                return () => {
                    clearInterval(interval);
                };
                }, []);
            
        

Always return a cleanup function. Missing this causes a useEffect cleanup memory leak.

2. Removing Event Listeners Safely

Leaky Event Listener

            
                useEffect(() => {
                const subscription = navigation.addListener('focus', () => {
                    console.log('Focused');
                });
                }, []);

            
        

Fixed Event Listener Code

            
                useEffect(() => {
                const subscription = navigation.addListener('focus', () => {
                    console.log('Focused');
                });
                
                return () => {
                    subscription.remove();
                };
                }, [navigation]);
            
        

This prevents the event listeners from leaking, a problem React Native apps commonly face.

3. Cleaning Up Timers, Promises & Async Tasks

Async Task Leak

            
                useEffect(() => {
                fetchData().then(setData);
                }, []);
            
        

Safe Async Cleanup

            
                useEffect(() => {
                let isMounted = true;
                
                fetchData().then(data => {
                    if (isMounted) {
                    setData(data);
                    }
                });
                
                return () => {
                    isMounted = false;
                };
                }, []);

            
        

This avoids state updates after unmount, a hidden React Native memory leak.

4. Optimizing FlatList & Image Memory Usage

Unoptimized FlatList

            
                <FlatList
                data={items}
                renderItem={renderItem}
                />
            
        

Optimized FlatList (Recommended)

            
                <FlatList
                    data={items}
                    renderItem={renderItem}
                    keyExtractor={item => item.id}
                    removeClippedSubviews
                    windowSize={5}
                    initialNumToRender={10}
                    />
            
        

For images, always use caching and resizing:

            
                <Image
                source={{ uri: imageUrl }}
                style={{ width: 100, height: 100 }}
                resizeMode="cover"
                />
            
        

These fixes significantly reduce memory pressure and help fix memory leaks in React Native large lists.

Why These Fixes Matter for Businesses & Startups?

• Fewer crashes = better user retention.
• Lower memory usage = smoother performance.
• Better reviews = higher app store rankings.

Strong React Native performance optimization directly impacts revenue and scalability.

Here’s the Complete GitHub Code to Detect & Fix Memory Leaks in React Native.

Our Proven Approach to React Native Memory Leak Detection & Fixes

• We analyze JavaScript and native memory together to ensure complete React Native memory leak detection coverage.
• Our experts profile memory usage in React Native apps using Flipper heap snapshots and navigation stress testing.
• We fix useEffect cleanup memory leaks, event listener leaks, and background task issues at the root level.
• Our team focuses on prevention strategies to stop memory leaks from reappearing in future app updates.

Want a Scalable React Native Application? Contact Us Now!

How Do You Prevent Memory Leaks in Large-Scale React Native Apps?

For large apps, prevention is more important than fixing later.

Architecture-Level Prevention Strategies

• Follow strict cleanup patterns in all components.
• Centralize event listeners and subscriptions.
• Avoid unnecessary global state retention.

Safe Navigation & State Patterns

• Unsubscribe on screen unmount.
• Avoid storing heavy objects in global stores.
• Use memoization carefully.

Monitoring Memory in Production

• Track crashes and memory warnings.
• Analyze real-user memory patterns.
• Continuously improve React Native performance optimization.

This proactive approach helps prevent memory leaks that React Native apps face at scale.

Build Faster & Crash-Free React Native Apps

Memory leaks don’t just affect performance; they affect user trust, revenue, and scalability.

That’s why memory leak detection should be part of every React Native release cycle.

By using the right tools, patterns, and monitoring strategies, you can build fast, stable, and crash-free React Native apps.